Safety switch



Nov. 1, 1955 F. w. MURPHY ET AL SAFETY SWITCH Filed April 15, 1953 INVENTORS F WMu r v 71y .6. BY J7 Mur vh y M ATTORNEYS United States Patent Ofiice 2,722,576 Patented Nov. 1, 1955 SAFETY SWITCH Frank W. Murphy and Arthur C. Murphy, Tulsa, Girls.

Application April 13, 1953, Seriai No. 343,334

1 Claim. (Cl. Mitt-56) This invention relates to a safety switch for engines.

In internal combustion engines, particularly of the stationary type, the engines are frequently left unattended for various periods, and in the event of failure in the lubricating system, serious damage results to the engine before it is stopped. As these engines usually operate the ignition system from a magneto, the engine if equipped with a safety switch as embodied in Patent No. 2,358,729, issued September 19, 1944, will be stopped when the oil pressure reaches a predetermined low. It is an object of this invention to provide a means in combination with the safety switch shown in the patent supra wherein the grounded ignition circuit could be broken in order to permit starting the engine.

Another object of this invention is to provide a means for breaking the grounded ignition circuit which after starting of the engine will be automatically rendered ineffective so that the safety switch may operate in its normal manner.

With the above and other objects in view, our invention consists in the arrangement, combination and details of construction disclosed in the drawing and specification, and then more particularly pointed out in the appended claim.

In the drawing:

Figure l is a front elevation, partly broken away and in section; of a pressure gauge and switch structure having incorporated therewith a switch release means constructed according to an embodiment of this invention,

Figure 2 is a fragmentary sectional view taken on the line 2-2 of Figure 1,

Figure 3 is a fragmentary sectional view taken on the line 33 of Figure 2.

Referring to the drawing, the numeral designates generally a combined pressure gauge and safety switch structure which is of the type embodied in Patent No. 2,358,729, dated September 19, 1944. This safety switch structure includes a stationary and adjustable contact 11 which is extended through the side wall 12 of the housing 13.

The pointer 14 which indicates the liquid pressure forms the movable switch element, and pointer 14 has fixed thereto a contact member 15 which is adapted to engage contact 11 when the liquid pressure reaches a predetermined low.

In order to provide a means whereby the pointer and movable switch member 14 may be disengaged from contact 11 so as to thereby break the grounded circuit which is connected with the magneto, I have provided a springpressed latch member 16 which is pivotally carried by a mounting 17. The latch member 16 is of substantially L-shape, being provided with a stem 18 which is pivotally mounted in the mounting 17, and a spring 19 constantly urges the latch member 16 to a released position, which is the full line position shown in Figure 1.

Pointer 14 has fixed thereon a keeper 20 with which the free end of the latch member 16 is adapted to engage when the latter is moved inwardly to a circuit breaking position. A latch operating lever 21 is fixed to the stem 18 and is disposed in confronting position with respect to a spring-pressed button or operator 22 which is slidable in a bushing 23. The bushing 23 is adapted to project through the housing 13 and is secured in the side wall 12 of the housing 13 by means of inner and outer nuts 24 and 25 respectively. The operator 22, which is slidable in the bushing 23, is constantly urged outwardly by means of a spring 26.

in the use and operation of this device, the gauge structure it) is connected with the lubricating or other liquid pressure system of an engine, and stationary contact 11 is connected, as shown in Fatent 2,358,729, to one side of the ignition system. Housing 13 is grounded to one side or" the magneto so that when contact 15 engages contact 11 the ignition circuit will be grounded and the engine will be stopped. This stopping of the engine occurs at a predetermined minimum or low pressure. After the engine has been stopped by grounding of the magneto circuit, the circuit can be opened by pressing the operator 22 inwardly so that latch member 16 will swing pointer 14 clockwise, with contact 15' disengaged from contact 11. The position at which latch member 16 holds pointer 14 disengaged from contact 11 is between the minimum and maximum position of the pointer so that when the engine starts and pressure is built up in the lubricating system, pointer 14 will be swung additionally clockwise or to the right. Further swinging of pointer 14 by liquid pressure will disengage pointer 14 from latch member 16 and the latter will thereafter be moved to a released position by means of spring 19. This attachment for the pressure gauge 16 will eliminate the necessity of a separate circuit breaking switch such as disclosed in Patent 2,358,729.

We do not mean to confiine ourselves to the exact details of construction herein disclosed, but claim all variations falling within the purview of the appended claim.

What is claimed is:

In combination, a pressure gauge having a movable pointer, a contact fixed on said pointer and constituting one side of a grounding switch, a fixed contact confronting said first-named contact and engageable with the latter when said pointer indicates a predetermined low pressure, said fixed contact constituting the other side of said grounding switch, a keeper fixed on said pointer, a normally released latch member engageable with said keeper for biasing said pointer toward a position in engagement with said first-named contact disengaged from said fixed contact, an operator for said latch member, and spring means for biasing said operator and hence said large member out of engagement with said keeper.

References Cited in the file of this patent UNITED STATES PATENTS 807,568 Mitchell Dec. 19, 1905 1,589,545 Newkirk June 22, 1926 1,654,102 Thompson Dec. 27, 1927 2,358,729 Murphy Sept. 19, 1944 

